Multiple &#34;a&#34; type display device having magnetically deflected cathode ray tube



Sept 8, 1970 J. HoLLANDl-:R ETAL 3,527,979'

MULTIPLE "A" TYPE DISPLAY DEVICE HAVING MAGNETICALLY DEFLECTEDCATHODE RAY TUBE 2 Sheets-Sheet 1 Filed July 16, 1968 Sept 8. 1970 J. HOLLANDER ETAL. 3,527,979

MULTIPLE "A" TYPE DISPLAY lDEVICE HAVING MAGNETICALLY DEFLECTED'CATHODE RAY TUBE Filed July 16, 1968 2 Sheets-Sheet 2 United States Patent Olce 3,527,979 Patented Sept. 8, 1970 U.S. Cl. 315-22 3 Claims ABSTRACT OF THE DISCLOSURE A multiple A type display device employing a raster technique.

This invention relates generally to the iield of cathode ray tube displays, and more particularly to an improved A type presentation.

A common type of display used in electronic countermeasures equipment is the A type of cathode ray tube. Normally, the `amplitude of horizontal deflection of the cathode ray tube lbeam is made proportional to a radiofrequency, and the vertical deflection is made proportional to the amplitude of a received signal. By Calibrating a horizontal base line, an operator can determine the frequency of the intercepted signal, and can judge the relative signal strength of the signal. Electrostatically deflected cathode ray tubes are very often used in this application. This is especially true where multiple A traces are required, that is to say where multiple tuning ranges must be simultaneously displayed. In these instances, a multigun electrostatic tube may be used. In such a tube, each gun is independent of the others, and can be used to present multiple A traces. Electrostatic tubes, however, have several disadvantages. Not only is the ratio of display tube useable area to overall tube length small, but the deflection sensitivity is inversely proportional to accelerating potential. Thus, an increase in accelerating potential, and hence in tube brightness, exacts a penalty in deflection sensitivity. For applications requiring short length, large screen area, and high brightness a magnetically deected cathode ray tube is more suitable.

Such a magnetic tube requires a yoke to deflect the beam. -For a single A trace, deflection can be achieved by a current-drive signal to the vertical and horizontal portions of the yoke. However, for multiple A traces, on a magnetically deflected tube, electronic switching of the single beam is required. This switching requirement imposes severe restrictions on the electrical parameters of the yoke. The yoke inductance must be made low to increase response time. This, however, complicates the yoke current-driver circuitry which must now supply an increasing amount of current to deflect the beam.

It is therefore among the principal objects of the present invention to provide a multiple A trace display device, in which the above mentioned disadvantages have been substantially eliminated.

Another object of the invention lies in the provision of an improved multiple A trace display device employing a raster technique to display the traces on a magnetically deflected cathode ray tube.

Another object of the invention lies in the provision of an improved A trace display device permitting the use of magnetically deflected cathode ray tubes while conserving circuit power and reducing circuit complexity.

These objects, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claims.

In the drawings, to which reference will be made in the specication;

FIGS. la and 1b are a schematic diagram of an embodiment of the invention.

FIG. 2 is a schematic View of the face of the display tube which forms a part of the disclosed embodiment.

Briefly stated, the basic techniques employed in the invention are a refinement of standard television practice. A 50-cycle sawtooth sweep signal is generated by dividing down from the input 40G-cycle power line normally available in aircraft installations, Other means, may be used, where other sources of power are available. The sawtooth signal deects the cathode ray tube beam in a horizontal direction. A 20-kilocycle sawtooth sweep signal generator is also provided to deflect the cathode ray tube beam in a vertical direction. In essence, the cathode ray tube sweeps are reversed from that of a normal television presentation. To display an A presentation of received signals against RF frequency, the vertical sweep lines are intensied in length proportional to received signal strength. This is accomplished using two comparators. In the absence of a signal, the two levels to the comparators (position and base line width) are adjusted to display a ne line across the width of the cathode ray tube.

When a video signal is received, it is converted to a D-C level which controls the duration of a pulse Width modulated one shot multivibrator. This results in a wider unblanking pulse at the output of an AND gate. The cathode ray tube is thereby unblanked in proportion to received signal strength. Additional traces on the cathode ray tube are presented by providing additional channels. The number of traces that can be displayed is limited only by the ability of the operator to interpret large numbers of traces simultaneously displayed.

This technique is also applicable when used in systems requiring both automatic and manual modes of operation. When any tuner is selected for manual operation, an unblanking signal is generated by comparing the SO-cycle tuner sweep and the D-C voltage corresponding to manual operation. The resulting pulse is used to enable the AND gate to intensify the screen at the time corresponding to the manual frequency. The total circuitry is repeated for all other channels. A common OR gate then effectively sums all the channel unblanking levels, and transmits them to the cathode ray tube grid. The cathode ray tube is preferably of the type employing an aluminized phosphor to achieve high brightness with the required persistence.

With the foregoing discussion in view, reference may be made to the disclosed embodiment shown in the drawing, wherein the device, generally indicated by reference character 10, includes a plurality of tuner modules, one of which is indicated by reference character 11. Each module includes a plurality of tuner modules, one of which is indicated by reference character 11. Each module includes a tuner signal source 12, a mode selector means 13, and manual tuning means 14.

The tuner signal source 12 feeds a stretch circuit 15, the output of which is fed to a buffer 16a and a pulse width modulated 1shot multivibrator 16h. The output of the multivibrator is fed to an AND gate 17.

The mode selector means 13 is connected to a comparator 18, the output of which is connected to a differentiator 19, in turn connected to one shot multivibrator 20, the output of the multivibrator being connected to the AND gate 17, the comparator, diierentiator and multivibrator functioning when the device is set for manual operation.

When on automatic operation, the mode control switch 13 transmits the 50-cycle sweep simultaneously to both the tuner and the yoke of the display, thereby creating a display having a point corresponding to each discrete frequency.

An input power source 2S supplies alternating current to the countdown circuit 26, the output of which is connected to a 50cycle sweep generator 28 in turn feeding the yoke driver circuit 29. The output of this circuit is connected to the yoke 30 of the cathode ray tube 31which forms the display.

The 20 kc. sweep generator 32 is connected to the yoke driver circuit to provide vertical deflection, as described hereinabove. This signal is connected to a comparator 27, the output of which feeds a pulse width modulated one shot multivibrator 1Gb, the output of which is connected to AND gate 17. Vertical tube position means 34 is also connected to the comparator 27.

The output of the AND gate 17 passes through a buffer 36 to an OR gate 37, which also receives the output 38 and 39 of additional channels (not shown). This output is fed to a further amplication stage at 41, the output of which is fed to an unblanking amplilier 43, and thence to the tube 31.

Referring to FIG. 2 in the drawing, the face 47 of the tube 31 displays vertical parallel lines 49 formed by the raster. A base line 50 is formed by unblanking the points on each line at a common horizontal level. With the occurrence of a signal on a given channel, that portion of the line above the base line is unblanked to provide a portion visible by the operator representative of signal strength received in that channel.

During operation, the base line 50 is located vertically by adjustment of the vertical tube position means 34 to desired location, and the base line with control 35 is adjusted to allow unblanking of the raster suiicient to form a dot on each sweep of the 20 kc. generator on each scanning line, as indicated in FIG. Z in the drawing. On the occurrence of a video signal, further unblanking above the base line width occurs in proporation to signal strength.

We wish it to be understood that we do not consider the invention limited toy the precise details of structure shown and set forth in this specification, for obvious modications will occur to those skilled in the art to which the invention pertains.

We claim:

1. A cathode ray display device for simultaneously presenting a plurality of linear displays corresponding to receive signals in terms of indicated frequency and amplitude comprising: at least one tuner covering a preselected frequency range, a cathode ray tube, a beam deflection circuit for producing a raster for displaying a number of parallel lines along a desired axis, a sweep generator, a

comparator, a pulse width modulated one-shot multivibrator controlled by the output of said tuner; said comparator triggering said pulse width modulated one-shot multivibrator to unblank points on said parallel lines to form a base line on the face of said cathode ray tube, the occurrence of a signal from said tuner serving to further unblank a discrete segment of said raster to a degree corresponding to received signal strength.

2. Structure in accordance with claim 1, including a plurality of tuners and corresponding comparators and multivibrators, and AND gates connecting each of said tuners to said cathode ray tube, each of said tuners covering a frequency range corresponding to a discrete portion of said base line.

3. Structure in accordance with claim 2, in which said base line is horizontally arranged relative to a viewer.

References Cited UNITED STATES PATENTS 2,775,757 12/1956 Ellsworth 343-5 X RICHARD A. FARLEY, Primary Examiner I. G. BAXTER, Assistant Examiner 

